Hydraulic fluids



United States Patent 'ce 3,283,029 HYDRAULIC FLUIDS MichelLouis Lucien Brilland and Pierre Anthelme Tardy, Le Havre, France, assignors to Compagnie Francaise de Raflinage, Paris, France No Dram'ng. Filed Sept. 25, 1963, Ser. No. 311,321

Claims priority, application France, Sept. 26, 1962, 910,547, Patent 1,357,634 4 Claims. (Cl. 260-6839) This invention relates to hydraulic fluids such as are used in very many control systems, for example brakes for aircraft undercarriages, signs and signals and, in general, any form of mechanical or electromechanical device in which a force is transmitted by a liquid, and in hydraulic and hydropneumatic' damping devices.

Fluids for uses of this kind must comply with several conditions which :are usually as follows: their tireezing point must be low enough for them to stay liquid down to very low temperatures, and their boiling point must be high enough for them not to boil in operation. They must have a high viscosity index, to ensure that their viscosity varies little with temperature and that viscosity remains low at very low temperatures. Also, they must not attack the metals and alloys of the fluid circuits, nor must they dissolve nor cause to swell the various rubbers and elastomers used for gaskets.

The limit characteristics of hydraulic fluids are laid down in stringent specifications such as, for instance, the

specification of United States Automotive Engineer Society, such :as specifications SAE 70 R, SAE 71 R the latter relating more particularly to mineral-based fluids.

It is diflicult to find purely hydrocarbon bases of a petroleum origin which meet these specifications, and so there have been many suggestions for formulae based on synthetic organic compounds, such :as silicone oils, glycols, glycol polyethers and so on. However, products of this kindare usually expensive, and so from the cost point of view petroleum products have a definite advantage.

In the petroleum industry it is very common to polymerise propylene, isobutylene and n-butylenes on acid catalysts, such as phosphoric acid deposited on carbon, or on kieselguhr or other supports. This treatment leads to homopolymers (dimers, trimers, tetrarners, pentamers) and/ or heteropolymers which are complex iso-olefin mixtures. Of the many known uses of such products, it may 'be mentioned that diisobutylene after hydrogenation to 2,2,4-trimethylpentanc, is classified as a high octa-ne fuel, that the dodecenes forming the butylene trimers ora.nd preferably-the propylene tetnamers, are used in the manufacture or dodecylbenzene, which is a detergent base, that the heptenes resulting from the lcopolymerisation of propylene and butylene or of polymers, and the octenes and nonenes originating respectively from the dimersation and trimerisa-tion of butylenes and propylene, are useful basis for Oxo synthesis.

The research in connection herewith has shown that very valuable hydraulic fluid bases can be formed by isoparaflin mixtures having from 12 to 18 carbon atoms and resulting from hydrogenation of the polymers or oligomers of light olefins, such as propylene or the butylenes or isobutylene.

This invention has for its object, in the first place to provide hydraulic fluids of this kind, which are distinguish'ed more particularly by their low freezing point and their high viscosity index, and in the second place to provide a process for the preparation of such fluids from the polymers specified. The underlying idea of the process according to the invention is:

(1) To separate in such polymers by distillation a 3,283,029 Patented Nov. 1, 1966 cut having an initial point above 175 C. and preferably distilling at from 200 to 300 C. and meeting the specifications of the required fluid as regards both the initial and final point of distillation of the A.S.T.M. (American Society for Testing Methods).

Particular attention should be paid to adjusting the initial point to obtain a flash point in accordance with the specifications, and to the final point, to adjust the viscosity to the required level.

(2) And then to effect total hydrogenation of the ethylene bonds of such cut. Within the scope of the invention, this hydrogenation can be performed by any known means, more particularly on a nickel or nickel molybdate catalyst, and continues until a saturated prod uct having a substantially zero bromine value is yielded.

The following examples illustrate processes to provide hydraulic fluid bases according to this invention.

Example I A mixture of polymers having an initial point of 262 C. and a final point of 312 C. and a density D 0.821 is prepared by polymerisation of propylene on a phosphoric-acid-based catalyst on kieselguhr at 190 C. at a pressure of 60 'kg./cm. This product is fractionated to separate a cut having an initial point of 257 C., a final point of 292 C, a density of 0.817 at 15 C. and a bromine value of 74.5. The product is hydrogenated continuously on a nickel catalyst at a temperature of 190 C. and a pressure of 10 km./cm.

The hydrogenate thus produced can be used directly as a hydraulic fluid base with the following characteristics:

Pour ipoint A.S.T.M., C.

This product is satisfactorily inert to various kinds of synthetic rubber, as the following test shows where a specimen experienced, :at 70 C. for 168 hours, the compared action 015:2! control spindle and of the foregoing fluid according to the invention.

The following Table I shows the measured increases in size of the specimens as caused by the two liquids.

TABLE I Hydraulic fluid Reference Specimens base according to Spindle the invention Synthetic rubber No. 1 11.3% Vol 29.5% Vol. Synthetic rubber No. 2-.. 3.7% Vol 40.0% Vol. Synthetic rubber No. 3- 2% Vol 0.4% Vol.

Without departing from the scope of this invention, the total polymers or copolymers resulting from polymerisation of the olefins can be hydrogenated to yield a mixture of saturated isoparafiins having a zero bromine value, w hereafter this mixture is subsequently [fractionated to separate a out having an initial point above C. and complying as nearly as possible with the distillation, flashpoint and viscosity specifications of the required hydraulic fluid.

The hydraulic fluid bases formed by hydrogenated polymers, as hereinbefore described, are compatible with the normal viscosity dopes and with antiwear additives.

By way of example, the following Table II gives the characteristics of the two hydraulic fluids (compositions 3 A and B) prepared from such bases with the appropriate dopes, and which are more particularly intended to be used in hydnaulic circuits of automobiles. 70 h. with- Percent swelling Spindle 33 TABLE II 5 Brake liquid T 25.8 Brake liquid M 262 Base No. 1 Composi- Composi- Brake liquid N 52.3

tion A tion B Example II c lgfijif??? 100 3 5,5 By polymerisation of propylene on a phosphoric-acidi g late or based catalyst on kieselguhr at 190 C. at a pressure of i 0 54 kg./cm. there is obtained, after fractionation a mix- Polymeigmrylate 0! O 12 5 ture of polymers having an initial point of 199 C., a final Tricresyiiifibbliitf 1 "1 point of 313 C., adensity D =0.800 and a bromine g g g w 1 1 15 value of 81. The product is hydrogenated continuously Density at 15" 0 0.826 0. 323 on ,a nickel catalyst at a temperature of 190 C. at a Distillation A S T M ressure of k0 /cm 2 0 246 247 246 p iiig i fg fif 270.5 272.5 274.5 The hydrogenated fraction thus obtained has the (fol- F2181 298 299 307 lowing characteristics: vlscoslilz gs) 420 1 200 1 100 liw Fjjijjjjj 4.58 17.06 15. 48 ii at C 0-791 305 i g 5 g: Refractive index at 20 C 1.4395 v c sit 556;" j 207 21 5.6 DISHIIaPPH ;oi i i m w .s. o 33 3g 2% Initial point, C. 215 S1]?:)hl 1 l g.p .m?i? 1i o.0s 0.05 25 9 1 235 Final point, C. 270 Flash point (Cleveland), C. 90 These compositions behave well in relation to ynth lc Viscosity at 40 3,, 55 rubber, as the following Ta le H sho s; Table III 8 1 Viscosity at +100 (3,, cs 2.41 the swelling of a synthetic rubber specimen f r being Pour point A,S,T,M, c, 70 treated at 121 C. for 70 hours with the base and the Aniline point c, 37 v 'xture and with a reference s indle and vaniif ig f $3 brsake liquids p This product, mixed in suitable proportions with the mm hydrogenate of Example I, provides a base for hydraulic TABLE HI fluids more particularly useful in aviation; V

The following Table IV gives the characteristics of two Treatment at 121 C. for hydraulic fluids (compositions C and D) prepared from 70 h 'with Percent swelling this base (base No. 2) which are compared with the Ba e 14.7 principal requirements of the American specification "Composition A 18.7 MlL-H-5 606A (Hydraulic Fluid-Petroleum Base-Air- Composition B 17.6 40 craft).

TABLE IV Base Composi- Composi- American N0. 2 tion 0 tion D Specification MIL HSGOGA Composition, wt. percent:

1 Mineral base- 100 81.5 80.5 (2) Additives:

Polymethacrylate 01' alkyl 16 5 roiiinfiii'ifyii'oibiii i z 18,5 Tricresyl phosphate 0. 5 0. 5 Trialkyl phenol 0. 5 0. 5 Characteristics:

Density at 15 C 0. 797 0.820 0.817 Distillation A.S.T.M

Initial point C 219 Point 247 Final Point 285 Viscosity (cs.) at:

40 C 92 419, 8 500 maximum. 11.--- 13.99 14. 20

0 F 10. 52 10.23 10 minimum. 210 F 5. 94 5.30 Viscosity index 222 224 Pour point ASTM C.) -68 68 59 maximum. Flash point Cleveland C. s l 98 96 96 93 Aniline point 0.) s9. 4 88 s Swelling of synthetic rubber +16 +16.6 +19 to +26.5.

(168 h. at 70 G.)-Change in volume (percent). Test for Oxidation Corrosion (168 h. at 121 C.)-Change in weight of test pieces alter test (mg/c1113):

0.00 0.00 -o.03 -0. 02 Magnesium 0. 00 Change in viscosity of oil at +6.5

F. alter test (percent). Change in acid index of oil alter +0. 04

test (mg. KOH/g.).

We claim:

1. A process for the preparation of stable mixtures of saturated petroleum hydrocarbon polymers having low freezing points and high boiling points and high viscosity indexes, said mixtures being substantially non-corrosive to metals and substantially inert to rubbers and like elastomers and being particularly adapted for use as hydraulic fluids, which comprises the steps of subjecting a mixture of light olefins to catalytic polymerization to form a mixture of olefinic polymers substantially all of which contain about 12 to 18 carbon atoms per molecule, separating from said mixtures of polymers a fraction having a boiling range of about 200 to 300 C., and subjecting said separated fraction to catalytic hydrogenation until said olefiriic polymers have a substantially Zero bromine value.

2. A process as recited in claim 1 in which said light olefins are substantially all selected from the group consisting of 3-carbon and 4-carbon olefins.

3. A new composition of matter particularly adapted for use as hydraulic fluids and comprising a mixture of branched chain petroleum hydrocarbon polymers having References Cited by the Examiner UNITED STATES PATENTS 2,961,330 11/1960 Meriwether 26068 3.9 3,003,009 10/ 1961 Gurd et al 260683.9 3,100,808 8/1963 Dyer 208-18 3,156,736 10/ 1964 Southern et a1 260683.9

DELBERT E. GANTZ, Primary Examiner.

S. P. JONES, Assistant Examiner. 

1. A PROCESS FOR PREPPRATION OF STABLE MIXTURES OF SATURATED PETROLEUM HYDROCARBON POLYMERS HAVING LOW FREEZING POINTS AND HIGH BOILING POINTS AND HIGH VISCOSITY INDEXES, SAID MIXTURES BEING SUBSTANTIALLY NON-CORROSIVE TO METALS AND SUBSTANTIALLY INERT TO RUBBERS AND LIKE ELASTOMERS AND BEING PARTICULARLY ADAPTED FOR USE AS HYDRAULIC FLUIDS, WHICH COMPRISES THE STEPS OF SUBJECTING A MIXTURE OF LIGHT OLEFINS TO CATALYTIC POLYMERIZATION TO FORM A MIXTURE OF OLEFINIC POLYMERS SUBSTANTIALLY ALL OF WHICH CONTAIN ABOUT 12 TO 18 CARBON ATOMS PER MOLECULE, SEPRATING FROM SAID MIXTURES OF POLYMERS A FRACTION HAVING A BOILING RANGE OF ABOUT 200* TO 300*C., AND SUBJECTING SAID SEPARATED FRACTION TO CATALYTIC HYDROGENATION UNTIL SAID OLEFINIC POLYMERS HAVE A SUBSTANTIALLY ZERO BROMINE VALUE. 